An Equine Wound Model to Study Effects of Bacterial Aggregates on Wound Healing

Abstract

Objective: Relevant animal models to study effects of bacterial aggregates on wound healing are lacking. We aimed at establishing an equine wound model with bacterial aggregates to investigate the impact of bacterial inoculation on normal (thorax) and impaired (limb) wound healing. Approach: Wounds were created on three limbs and both thorax sides of six horses. Twelve out of 20 wounds per horse were inoculated with 10 4 Staphylococcus aureus and 10 5 Pseudomonas aeruginosa on day 4. Healing was monitored until day 27 by clinical assessment, including wound scoring, surface pH measurements, and digital photography for area determination. Biopsies were used for bacterial culture and for peptide nucleic acid fluorescence in situ hybridization to detect bacterial aggregates. Results: Inoculated limb wounds healed slower than noninoculated limb wounds from day 10 onward ( p < 0.0001). Inoculated and noninoculated thorax wounds healed equally well and faster than limb wounds. The odds ratio of detecting bacterial aggregates in inoculated limb wounds was 7.1 (2.4–21.0, p = 0.0086) compared with noninoculated limb wounds and 36.2 (3.8–348, p = 0.0018) compared with thorax wounds. Innovation: This equine wound model with bacterial aggregates might be superior to other animal wound models, as both normal and impaired healing can be studied simultaneously. In this model, many aspects of wound healing, including novel treatments, may be studied. Conclusions: The impaired healing observed in inoculated limb wounds may be related to the persistent bacterial aggregates. Both in capability of clearing inoculated bacteria from the wounds and in healing pattern, thorax wounds were superior to limb wounds.

Biofilm and Equine Limb Wounds

“…We have recently shown in an equine experimental wound model that biofilms were present in equine limb wounds but not in body wounds [17]. Further, in a recent equine experimental wound model with bacterial inoculation, we found biofilms to negatively affect wound healing of distal limb wounds but not body wounds [18]. Based on these initial findings of biofilms in equine limb wounds and on several similarities between equine and human impaired wound healing [19][20][21], there is a good reason to expect biofilm formation to also play a role in the delayed healing of limb wounds in horses.…”

“…There is only a very sparse bulk of literature on biofilm-related infections and their diagnosis and management in veterinary clinical medicine [11][12][13][14][15][16][17][18][49][50][51]. To understand the subject, we currently have to broaden our view and look to other scientific areas (such as experimental medicine, biofilm research, and human clinical medicine).…”

Colloidal Iron Oxide Formulation for Equine Hoof Disinfection

“…Pseudomonas aeruginosa (gram-negative) was chosen to demonstrate the specific mechanism of IA and its efficiency on both gram-positive and gram-negative bacteria. It is noteworthy that, both these species, are commonly associated with tissue infections [ 21 ]. The results showed that IA was able to completely suppress the bacterial growth on all the tested microorganisms.…”

Epithelial‐to‐mesenchymal transition and keratinocyte differentiation in equine experimental body and limb wounds healing by second intention

“…Biopsies were available from a study involving experimental excisional dermal wounds in six adult horses . Horses were clinically healthy and were without any signs or history of dermatological diseases or injuries.…”

“…The experimental procedure is described in detail elsewhere . In brief, the horses had four wounds (2 × 2 cm) created on the lateral aspect of the metatarsus/‐carpus (limb) and on the lateral thoracic wall (body).…”